Konzo is a self-limiting central motor-system disease associated with food dependency on cassava and low dietary intake of sulfur amino acids (SAA). Under conditions of SAA-deficiency, ingested cassava cyanogens yield metabolites that include thiocyanate and cyanate, a protein carbamoylating agent. We studied the physical and biochemical modifications of rat serum and spinal cord proteins arising from intoxication of young adult rats with 50-200 mg/kg linamarin, or 200 mg/kg sodium cyanate (NaOCN), or vehicle (saline) and fed either a normal amino acid- or SAA-deficient diet for up to two weeks. Animals under SAA-deficient diet and treatment with linamarin or NaOCN developed hind limb tremors or motor weakness, respectively. LC/MS-MS analysis revealed differential albumin carbamoylation in animals treated with NaOCN, vs. linamarin/SAA-deficient diet, or vehicle. 2D-DIGE and MALDITOF/MS-MS analysis of the spinal cord proteome showed differential expression of proteins involved in oxidative mechanisms (e.g. peroxiredoxin 6), endocytic vesicular trafficking (e.g. dynamin 1), protein folding (e.g. protein disulfide isomerase), and maintenance of the cytoskeleton integrity (e.g. α-spectrin). Studies are needed to elucidate the role of the aformentioned modifications in the pathogenesis of cassava-associated motor system disease.

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Lower motoneuron abnormalities have been extensively documented in the murine model of familial amyotrophic lateral sclerosis, whereas information on corticospinal neurons in these mice is very limited. We investigated 1) mRNA levels of inflammation-related molecules in the deep layers in which corticospinal neurons reside, 2) corticospinal neurons labeled from tracer injections in the corticospinal tract at the cervical level, 3) axonal damage revealed by A-amyloid precursor protein accumulation, and 4) glial cell activation in the sensorimotor cortex of presymptomatic and endstage superoxide dismutase (SOD)-1 (G93A) mice. We demonstrated induction of inflammatory gene transcripts in the deep layers, early and progressive shrinkage of corticospinal cell bodies and activation of surrounding astrocytes and microglia with upregulation of major histocompatibility complex class I antigen. Accumulation of A-amyloid precursor protein in proximal axonal swellings indicating axonal injury was also evident at the terminal stage in the motor cortex and internal capsule. Glial and axon changes were not observed elsewhere in the cortex. These data reveal that the entire motor circuit is affected in this murine amyotrophic lateral sclerosis model as it is in human amyotrophic lateral sclerosis. Sensorimotor cortical inflammation and progressive corticospinal cell body and fiber damage may reflect transsynaptic signaling of damage from lower motoneurons.

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